In the preparation of a photographic material, a support is usually coated with one or more layers comprising an aqueous solution of a hydrophilic colloid binder, such as gelatin. Such layers include, for example, silver halide emulsion layers, intermediate layers, antihalation layers, filter layers, antistatic layers, protective layers, and the like. For multilayer materials, the layers may be coated simultaneously, as described in U.S. Pat. Nos. 2,761,791 and 3,508,947.
In the preparation of hydrophilic colloid layers, the coating solutions must be coated uniformly with a minimum of repellency spots, or repellencies. A repellency is a coating unevenness, such as a round, oval, or comet-shaped indentation or crater in the layer or layers. Repellencies are often caused by the presence in the coating composition of finely-divided insoluble materials in the form of addenda, impurities, or contaminants that are surface active. Solutions coated in the preparation of photographic materials often contain dispersed insoluble photographic addenda, such as organic solvents, or addenda to alter certain physical properties, such as lubricants. Many of these addenda are capable of imparting repellencies to coated layers.
Photographic gelatin may contain insoluble residues of certain naturally-occurring animal fats and fatty acids, which can impart repellencies to the coated layer. Also, surface active contaminants may be introduced from external sources during preparation of the coating composition or during coating. For example, a layer may be contaminated during or immediately after coating by various oils used to lubricate the coating apparatus.
A wide variety of surface active agents have been suggested for use as coating aids to control the uniformity of photographic layers. For example, Japanese Kokai No. 49/046733 describes the use of certain fluoroalkyl sulfosuccinates as coating aids for photographic materials. These compounds, however, often do not prevent repellencies caused by surface active materials having low surface tension properties, such as silicone fluids used as lubricants and sealants.
It would therefore be highly desirable to provide a coating aid for photographic compositions that effectively reduce repellencies, especially those caused by materials from external sources, such as silicone fluids used as lubricants and sealants.